Which risk factors determine cartilage thickness and composition change in radiographically normal knees? - Data from the Osteoarthritis Initiative

Objective: Therapy for osteoarthritis ideally aims at preserving structure before radiographic change occurs. This study tests: a) whether longitudinal deterioration in cartilage thickness and composition (transverse relaxationtime T2) are greater in radiographically normal knees "at risk" of incident osteoarthritis than in those without risk factors; and b) which risk factors may be associated with these deteriorations. Design:755 knees from the Osteoarthritis Initiative were studied; all were bilaterally Kellgren Lawrence grade [KLG] 0 initially, and had magnetic resonance images available at 12- and 48-month follow-up. 678 knees were "at risk", whereas 77 were not (i.e., non-exposed reference). Cartilage thickness and composition change was determined in 16 femorotibial subregions, with deep and superficial T2 being analyzed in a subset (n = 59/52). Subregion values were used to compute location-independent change scores. Results: In KLG0 knees "at risk", the femorotibial cartilage thinning score (-634 +/- 516 mu m) over 3 years exceeded the thickening score by approximately 20%, and was 27% greater (p < 0.01; Cohen D -0.27) than the thinning score in "non-exposed" knees (-501 +/- 319 mu m). Superficial and deep cartilage T2 change, however, did not differ significantly between both groups (p >= 0.38). Age, sex, body mass index, knee trauma/surgery history, family history of joint replacement, presence of Heberden's nodes, repetitive knee bending were not significantly associated with cartilage thinning (r2<1%), with only knee pain reaching statistical significance. Conclusions: Knees "at risk" of incident knee OA displayed greater cartilage thinning scores than those "nonexposed". Except for knee pain, the greater cartilage loss was not significantly associated with demographic or clinical risk factors.